New research has confirmed one of the worst nightmares of climate science: the instability of the East Antarctic ice sheet.

This vast mass holds enough water to raise sea levels by 53 meters (approximately 174 feet) worldwide. And researchers have confirmed that one stretch of the southern polar coastline has melted many times in the past: by enough to raise sea levels by three to five meters (approximately 10 to 16 feet).

A rise of just one meter would render at least 100 million coast dwellers homeless.

The latest study confirms that suspicion. “It turns out that for much of the East Antarctic Ice Sheet’s history, it was not the commonly perceived large stable ice sheet with only minor changes in size over millions of years,” said Sean Gulick of the University of Texas Institute for Geophysics, one of those who led the study.

“Rather, we have evidence for a very dynamic ice sheet that grew and shrank significantly between glacial and interglacial periods. There were also often long intervals of open water along the Sabrina Coast, with limited glacial influence.”

“We are already seeing the effects of rising seas caused by melting ice sheets and ocean warming. There is enough ice in our study region alone to raise global sea level by as much as 15 feet. This, in isolation, would be catastrophic to Florida.”

But real estate investors and citizens who put their money into Florida are not likely to get any long-term certainty: nor are the hundreds of millions of people who dwell in low-lying communities from Bangladesh to the Nile Delta, from the coral atolls of Kiribati in the Pacific to the polders of the Netherlands in Europe.

“There’s a lot of ambiguity in post-2050 projections of sea-level rise and we may have to live with that for a while,” said Robert Kopp, director of the department of earth, ocean and atmospheric sciences at Rutgers University. “We could end up with 8 feet of sea level-rise in 2100, but we’re not likely to have clear evidence for that by 2050.”

“We’re making progress, but we still don’t know exactly when these processes might kick in, and how fast sea level might rise if they do. The ice shelves are the key.

“They hold back the flow of Antarctic ice toward the ocean, so we don’t want to lose them. The problem is, they don’t last very long when they are sitting in warm water or if they are covered with summer meltwater, so keeping global temperatures in check is critical.”